Abstract: The invention relates to a method of determining whether a subject is at an increased risk of developing or having ovarian cancer or being a carrier of a germline BRCA1 and/or BRCA2 mutation. The method may comprise determining whether the percentage contribution of lactic acid-producing bacteria to the bacterial load of a sample obtained from the lower genital tract of the subject is more or less than a percentage threshold level. The subject is at increased risk if the percentage contribution of lactic acid-producing bacteria to the bacterial load of the sample is less than the percentage threshold level. Alternatively, the method may comprise determining the pH of a sample obtained from the lower genital tract of the subject. The subject is at increased risk if the pH is higher than a pH threshold level.